This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A279846 #11 Mar 12 2017 16:17:52 %S A279846 1,31,37,43,46,61,67,73,79,85,91,106,109,121,127,133,136,145,151,157, %T A279846 166,169,181,199,211,217,226,232,235,241,253,265,271,274,277,289,295, %U A279846 301,307,313,316,325,331,337,343,361,379,391,397,406,409,421,433,451,463,469,481,496,505,511 %N A279846 Numbers that are centered k-gonal numbers for three or more values of k. %C A279846 Numbers satisfying 1 + n*m*(m+1)/2 for three or more values of (n,m), where n >= 0 m > 1. %C A279846 Numbers in this sequence appear in A101321 at least four times (because the second column contains every positive integer). %H A279846 Daniel Sterman, <a href="/A279846/b279846.txt">Table of n, a(n) for a(n)<1000</a> %e A279846 109 is in the sequence because 109 is a centered triangular number, a centered 18-gonal number, and a centered 36-gonal number. %Y A279846 Cf. A062712 (rough equivalent for polygonal numbers). %Y A279846 Cf. A101321 (table of all centered polygonal numbers). %Y A279846 Cf. A275340 (list of nontrivial centered polygonal numbers). %K A279846 nonn %O A279846 1,2 %A A279846 _Daniel Sterman_, Dec 20 2016